Survivors and families attend the president's address after a day of promoting their cause.

WASHINGTON — When President Obama implored Congress on Tuesday to take up the thorny issue of gun violence, he did so in the name of Nathaniel Pendleton Sr. and Cleopatra Cowley-Pendleton, whose 15-year-old daughter, Hadiya, was killed just two weeks ago in Chicago.

"They deserve a vote," he said in an escalating refrain echoed by legislators gathered for his State of the Union address. He recited other individuals and communities shattered by shootings, such as Aurora, Colo., and Newtown, Conn. Former Rep. Gabrielle Giffords (D-Ariz.), gravely wounded in a mass shooting in 2010, applauded by holding her hands together, one in the other, and rocking them as if she were clapping.

The Pendletons watched Obama's speech alongside First Lady Michelle Obama. More than two dozen other gun violence survivors and loved ones watched the address from the House gallery as guests of Democratic lawmakers.

Earlier Tuesday, there was a Senate hearing on gun violence, a Capitol Hill news conference, a White House briefing with Michelle Obama and meetings with individual representatives and senators. Those meetings will continue Wednesday.

The flurry of activity — coordinated mainly by Mayors Against Illegal Guns and the Brady Campaign to Prevent Gun Violence — aimed to illustrate the power of today's gun control movement.

"Politicians are beginning to understand that people that maybe they thought wouldn't mobilize or be active on this issue are going to mobilize and are going to be active," said Peter Read, whose 19-year-old daughter, Mary, was killed nearly six years ago in the Virginia Tech massacre. "And they realize they can't ignore it anymore."

At the Senate gun hearing Tuesday morning, Sen. Richard J. Durbin (D-Ill.) asked those in the audience who had been affected by gun violence to stand. Dozens of people, about half of the crowd, rose in silence.

"Look about this room," Durbin said. "Understand that the debate we have before us has affected so many lives."

Personal experience with gun violence does not necessarily mean support for tougher gun laws, said Suzanna Hupp, a witness at the hearing. Hupp lost her parents in a 1991 mass shooting in Killeen, Texas. She has since become an advocate for the right to carry concealed weapons — which was illegal in Texas at the time — and opposes gun control measures.

"When you opened the proceeding here, you asked all of the victims of gun violence to stand. And I hesitated," Hupp said. "Honestly, I don't view myself as a victim of gun violence. I view myself as a victim of a maniac who happened to use a gun as a tool. And I view myself as a victim of the legislators that we had at the time that left me defenseless."

But most of the gun violence victims in Washington this week come from the other side. In a quiet moment before the news conference, Read introduced himself to one of the newer advocates, Nathaniel Pendleton, and clasped both of his hands in his own.

The two fathers who had lost their daughters didn't say much, just held their handshake for an extended beat.

"Whether we've known each other for years … or just met them, we have a common bond, common objectives, because we've all been touched" by gun violence, Read said afterward. "You almost don't have to exchange any words to understand each other."

"It's kind of hard to explain to anyone that hasn't lived through it, but for anybody who has, no explanation is required," he added.